This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Phosphor/fluorescent particles have been used for quite some time. When shorter wavelength light strikes the phosphor particles, colored light with longer wavelength(s) is emitted, a process called down-conversion. The opposite effect also exists, where a phosphor particle is excited with an infrared or red light (longer wavelength) and emits blue/green/yellow color (shorter wavelength). The latter process is called up-conversion. Upconverting materials convert lower-energy light to higher-energy light, realized through excitation with multiple photons. Materials with upconverting properties are much less common than those with down-converting properties. Compared to conventional fluorescent reporters, upconverting phosphors are insensitive to the environment, do not photobleach, can be multiplexed to a greater degree, have no autofluorescence background, and are excited by much smaller, portable light sources. The goal of this project is to develop nanoparticles with photon upconversion properties, and apply them in sensitive cancer detection. Here we intend to a) optimize methods that can more systematically prepare upconverting nanoparticles, and b) to explore the applications of upconverting nanoparticles in prostate cancer detection. We expect these upconverting nanoparticles to become a highly sensitive signaling element. Studies have shown that early detection of cancers saves lives. In general, the smaller the tumor when diagnosed, the better the chance of being treated. The dramatically enhanced signal-to-noise ratio of the nanoparticles would allow us to catch the small number of cancer cells in the background of a large number of normal cells, a likely scenario at the very early stage of tumor development.